Graphene exfoliation in organic solvents and switching solubility in aqueous media with the aid of amphiphilic block copolymers

The successful exfoliation of graphite to graphene sheets in a liquid phase via tip sonication was achieved. A number of solvents were examined for several time periods and it was found that o-dichlorobenzene (o-DCB) and N-methyl-1,2-pyrolidone (NMP) are ideal solvents to exfoliate graphite and produce stable dispersions of graphene. The exfoliated graphene dispersions were characterized by complementary techniques including AFM, DLS, TGA and Raman. Furthermore, treatment of stable dispersions of exfoliated graphene sheets in NMP with poly[styrene-b-(2-vinylpyridine)] block copolymer, under acidic conditions, resulted in aqueous solubilization of graphene. Similar results were obtained, i.e. transfer of graphene from the organic to the aqueous phase, when the poly(isoprene-b-acrylic acid) block copolymer was added on exfoliated graphene in NMP.